Polymers of aniline and its derivatives are useful as antimicrobial agents and have good antistatic and free radical scavenging properties. These properties make them useful for the manufacture of antimicrobial, antistatic and antioxidant objects, and suitable for use in, for example, the health, food, packaging, water, paint, wood, textile, poultry, glass, paper, rubber, ceramic, seafood, sports, plastic and agricultural industries.
Adding substituents to polyaniline (PANI) is one way in which the various properties of the polymer can be improved. However, the synthesis of substituted PANIs is not always a straightforward matter. Any substituent introduced to the aniline building block needs to be compatible with the reagents used, which is not always possible under the traditionally robust oxidative polymerisation conditions used to form PANIs.
Carboxylated PANIs are one type of PANI derivative of particular interest due to their good antibacterial properties. Carboxylated PANIs can either be homopolymers, which could also be described as a poly(aminobenzoic acid) (poly ABAs) or copolymers, which could be considered as a PANI backbone bearing carboxylic acid groups on some of the aromatic rings. Figure 1 shows the probable structure of poly(2-aminobenzoic acid) and poly(3-aminobenzoic acid). Figure 2 shows the probable structure of copolymers of aniline and 2-aminobenzoic acid or 3-aminobenzoic acid, where X and Y are the numbers of repeat units.

However, producing PANI homopolymers and copolymers from aminobenzoic acid (ABA) monomers in good yield and purity is not a simple procedure. There are significant problems with the solubilities of ABAs. ABAs tend to be solids, unlike aniline itself or many substituted anilines (alkyl anilines like toluidine, alkoxy anilines like anisidine etc) which can be used directly in their liquid form. This low solubility impacts upon the cost of synthesis and the quality of the resultant polymers.
There thus exists a need to produce poly-ABAs (carboxylated PANIs) in high yield and in a cost effective manner, with high conversion of monomer units, short production time and high molecular weights.
It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.